The present invention relates to an electronic stringed instrument.
In an electronic stringed instrument, it is necessary that a fret position of a given string depressed by a player's finger is discriminated to specify a pitch of a musical tone to be produced, and at the same time, a picking timing is detected to determine timings of sounding of the musical tone.
A conventional method of detecting a fret position in the process for producing musical tones in such an electronic stringed instrument will be described with reference to FIG. 1. When a player depresses a string 1 with his finger at a desired position on a fingerboard so as to generate a specific musical tone, the string 1 is brought into contact with the specific fret and the length of the string 1 to be picked is determined. However, according to the conventional method, at this moment, the fret position is not discriminated. The fret position is discriminated after the player picks the string 1. More specifically, when the string 1 is picked, the string 1 vibrates in a period corresponding to the string length. The vibrations of the string 1 are converted by an electromagnetic pickup 2 into an electrical signal having a waveshape similar to the vibrations of the string 1. This electrical signal is waveshaped by a low-pass filter 3. A peak detector 4 detects the peak in amplitude of the waveshaped signal. A pulse converter 5 generates pulses in synchronism with the detection result of the peak detector 4. A pulse interval measuring circuit 6 measures an interval of pulses generated in synchronism with peak detection. The pulse interval measuring circuit 6 generates a digital signal corresponding to the pulse interval. A value represented by this digital signal corresponds to the fundamental frequency of the string 1 and also represents the position of the fret which which the string 1 is in contact. A tone generator 7 generates a musical tone signal on the basis of this digital signal. A sound system 8 produces a musical tone represented by the musical tone signal.
In the conventional arrangement described above, the position of the fret with which the string 1 is in contact is detected on the basis of the period of vibration of the picked string 1. At least a period corresponding to a possible maximum vibration period of the string 1 must be preset for detecting the peak. For example, a period of about 1/80 second is required for a typical six-string guitar. In addition, the vibrations of the string 1 immediately after picking have a large harmonic overtone component ratio, and this ratio causes variations in peak. Therefore, the initial peak is not used for discriminating the fret position, and the fret position is detected according to the second or subsequent peak at which the harmonic overtone component ratio is rapidly reduced. In the conventional arrangement, it takes a relatively long period of time until a musical tone is produced by the sound system after the player picks the string 1. The player experiences an unnatural feeling.
In an electronic stringed instrument having a plurality of strings 1, the vibration of the strings 1 are converted into electrical signals by electromagnetic pickups respectively corresponding to the strings 1. A magnetic field formed by each electromagnetic pickup 2 is adversely affected by not only the string 1 assigned thereto but also by adjacent strings. The fret position may therefore be erroneously discriminated.